The constituents of commercial chrysarobin / by H.A.D. Jowett, and C.E. Potter.

  • Jowett, H. A. D. (Hooper Albert Dickinson)
Date:
[1902]
Catalogue details

Licence: In copyright

Credit: The constituents of commercial chrysarobin / by H.A.D. Jowett, and C.E. Potter. Source: Wellcome Collection.

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    recrystallised substance, which agreed fairly well with the formula proposed, but no determination of the molecular weight was made. A crystalline acetyl compound was obtained which, however, on analysis gave numbers differing from those required for the formula C3oH2207(C2H30)4 (Found C = 67'5; required C = 68’5 per cent.). The subject was not again referred to for many years, and in the meantime the product has been sold indiscriminately as chrysarobin or chrysophanic acid. In 1899, Hesse (Annalen, 309, 32) examined chrysarobin and obtained results differing from those recorded by previous investi¬ gators. He showed that crude chrysarobin contained no chrysophanic acid, but was a mixture of two parts of chrysarobin, C15H1203, with one of its methyl ether. He was, however, unable to obtain chrysarobin free from its methyl ether, and arrived at this conclusion from indirect evidence. Eight specimens, varying in melting point from 152° to 174° and purified by different means, were analysed, but all yielded methyl iodide by Zeisel’s method, thus showing the presence of a methylated constituent. When the mixture was treated with hydrochloric or hydriodic acid, chrysophanohydroanthrone was obtained which was considered by Hesse to be isomeric with chrysarobin. On acetylation, however, the reverse change takes place, chrysophanohydroanthrone being converted into chrysarobin, since both yield the same triacetyl- chrysarobin. Chrysophanohydroanthrone and chrysarobin are both readily oxidised to chrysophanic acid, but if the impure chrysarobin is used a mixture of chrysophanic acid and its methyl ether results. Hesse thus regarded chrysarobin as the anthranole of chrysophanic acid. Before stating the results of the present investigation, we desire to point out that some of Hesse’s deductions are not in accordance with his observations, and further that simpler explanations than his can be given which are more in accordance with the facts. In the first place, the analyses of the different specimens of chrysarobin do not agree with the assumption that they consist of a mixture of chrysarobin and its methyl ether. If this were so, the percentages of carbon and hydrogen found should lie between those required for the two substances, whereas in all cases they are less than that required for either substance : Ci5Hi203 requires C = 75*0 ; H = 50 per cent. Ci5Hii03*CH3 requires C = 75*6; H = 55 per cent. Found C = 74-0 to 75 0; H = 5*0 to 5-3 per cent. It therefore follows that the methylated constituent must contain less than 75 0 per cent, of carbon. Secondly, chrysarobin is assumed by Hesse to be isomeric and not
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